CHEMISTRY GLOSSARY

polarography    →   polarografija

Polarography is a volumetric technique which is based on a diffusion controlled analyte travel to the surface of dropping mercury electrode (DME). The surface of the working electrode (dropping mercury electrode) is constantly renewed under dropping conditions and, thus, the conditions under which reaction takes place are readily reproducible. Depolarisation potential enables identification of ions present in the solution, and by measuring the diffusion current their concentration is calculated. Polarography was discovered in 1922 by the Czech chemist Jaroslav Heyrovský (1890-1967).

polonium    →   polonij

Polonium was discovered by Marie Curie (Poland) in 1898. Named for Poland, native country of Marie Curie. It is silvery-grey, extremely rare, radioactive metal. Soluble in dilute acids. Highly toxic. Severe radiotoxicity. Carcinogen. Polonium occurs in pitchblende. Produced by bombarding bismuth with neutrons. Used in industrial equipment that eliminates static electricity caused by such processes as rolling paper, wire and sheet metal.

polychlorinated biphenyls    →   poliklorirani bifenili

Polychlorinated biphenyls (PCB) are poisonous and carcinogenic compounds. They are pollutants of both live and inanimate environment, and they are used as insulation and refrigerating materials in transformers and condensers.

polydentant ligand    →   polidentantni liganad

Polydentant ligands contain more co-ordination points (can give more electron pairs) and they form complex ringlike structures (celate complexes) by replacing two or more monodentant ligands. That kind of ligand is EDTA which has 6 co-ordinational points and with metals it creates complexes, always in 1:1 ratio.

vapour pressure lowering    →   snižavanje tlaka pare

Vapour pressure is a colligative property of solutions. The vapour pressure of a solution is always lower than the vapour pressure of the pure solvent. Ratio of solution to pure solvent vapour pressures is approximately equal to the mole fraction of solvent in the solution.

polyester    →   poliester

Polyesters are copolymers formed by condensation polymerization of dicarboxylic acid (terephthalic acid) and a dialcohol, also called a diol (ethylene glycol).

polymer    →   polimer

Polymer is a substance composed of molecules of high relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass (monomers). In most cases the number of monomers is quite large and is often not precisely known. A single molecule of a polymer is called a macromolecule. Polystyrene is light solid material obtained by polymerisation of styrene (vinyl benzene).

polymerization    →   polimerizacija

Polymerization is a reaction of connecting many monomers in one long molecule whereby polymers are created.

polymorphism    →   polimorfija

Polymorphism is the ability of a solid substance to crystallise into more than one different crystal structure. Different polymorphs have different arrangements of atoms within the unit cell, and this can have a profound effect on the properties of the final crystallised compound. The change that takes place between crystal structures of the same chemical compound is called polymorphic transformation.

The set of unique crystal structures a given compound may form are called polymorphs. Calcium carbonate is dimorphous (two forms), crystallizing as calcite or aragonite. Titanium dioxide is trimorphous; its three forms are brookite, anatase, and rutile. The prevailing crystal structure depends on both the temperature and the external pressure.

Iron is a metal with polymorphism structure. Each structure stable in the range of temperature, for example, when iron crystallizes at 1 538 °C it is bcc (δ-iron), at 1 394 °C the structure changes to fcc (γ-iron or austenite), and at 912 °C it again becomes bcc (α-iron or ferrite).

Polymorphism of an element is called allotropy.

polypeptide    →   polipeptid

Polypeptides are peptides containing ten or more amino acid residues. The properties of a polypeptide are determined by the type and sequence of its constituent amino acids.